Research Highlight: Study Finds Toxic Pollutants in Fish Across the World’s Oceans

A new global analysis of seafood found that fish populations throughout the world's oceans are contaminated with industrial and agricultural pollutants, collectively known as persistent organic pollutants (POPs). The study by researchers at Scripps Institution of Oceanography at UC San Diego also uncovered some good news: concentrations of these pollutants have been consistently dropping over the last 30 years.

The findings, reported in the journal PeerJ, were based on an analysis by Scripps researchers Lindsay Bonito, Amro Hamdoun, and Stuart Sandin of hundreds of peer-reviewed articles between 1969-2012. The pollutants studied included older 'legacy' chemicals, such as DDT and mercury, as well as newer industrial chemicals, such as flame retardants and coolants.

“Based on the best data collected from across the globe, we can say that POPs can be anywhere and in any species of marine fish,” said Scripps biologist Sandin, a co-author of the study.

Although POPs were found in fish in all of the world’s oceans, the researchers say that concentrations in the consumable meat of marine fish are highly variable, where one region or group of fish may have concentrations of POPs that vary by 1,000-fold. The analysis revealed that average concentrations of each class of POP were significantly higher in the 1980s than is found today, with a drop in concentration of 15-30 percent per decade.

“This means that the typical fish that you consume today can have approximately 50 percent of the concentration of most POPs when compared to the same fish eaten by your parents at your age,” said Bonito, the lead author of the study.

The researchers also compared the results to federal safety guidelines for seafood consumption and found that the average levels of contaminants were at or below the health standards set by the U.S. Environmental Protection Agency (EPA). Mercury and PCBs (polychlorinated biphenyl) concentrations were at the EPA threshold for occasional human consumption, while concentrations of DDT were consistently much lower than the established threshold.

According to the authors, these results suggest that the global community has responded to calls to action, such as the Stockholm Convention, to limit the release of potentially harmful chemicals into the environment.

“The take-away message is that consumers should be very concerned about both ‘legacy’ and modern-day toxins in seafood,” said Jacob James, managing director of the Waitt Foundation, who funded the study. “While it’s an important finding that 'legacy' pollutants in seafood have dropped over the last 30 years, this is exactly what we should expect after decades of preventative regulation of these contaminants. Without similar regulations of modern pollutants, we will only see those levels go up over time.”

The authors caution that although toxic pollutant concentrations in marine fish are steadily declining, they still remain quite high, and that understanding the cumulative effects of multiple exposures to pollutants in seafood is necessary to determine the true exposure risk to consumers.